This invention relates to a process for separating organometallic compounds from liquid hydrocarbons. More particularly, this invention relates to a process for separating organolead compounds from liquid hydrocarbons.
As is well known, there is an increasing public and governmental interest in eliminating or at least significantly reducing the amount of pollutants emitted to the atmosphere as the result of combustion of various fuels in internal combustion engines. As is also well known, the amount of pollutants emitted to the atmosphere can be significantly reduced by passing the exhaust through one or more catalytic converters. Generally, however, the catalysts used in these converters are not effective in treating exhausts obtained from the combustion of leaded fuels. As a result, it has become necessary to provide unleaded fuels for use in vehicles equipped with such converters.
The production of lead-free or substantially lead-free fuels is, of course, well within the ordinary skill of the art. Delivery of such fuels to the consumer, however, cannot be as easily acccomplished. In fact, past experience with both lead-free and low fuels has indicated that intentional and/or inadvertent comingling of such fuels with leaded fuels renders such ultimate delivery impossible, at least, in 100% of the cases. Such comingling could occur in the pipelines of transport tankers as well as in storage tanks at terminals or retail outlets. The need, then, for a method, short of separate transport and storage facilities, which would ensure the delivery of a substantially lead-free fuel is readily apparent.
One such method which could be used is a separation method which would permit separation of relatively minor amounts of lead from the fuel stored at a terminal or a retail outlet (after transport) or from the gasoline in a tanker or pipeline or delivery truck prior to tranfer into a storage vessel. Indeed, several separation processes have, heretofore, been proposed for the separation of organolead compounds from gasoline. Generally, these have been two-step processes wherein the organolead compound is first converted to an insoluble or more readily absorbed form and thereafter separated either by absorption, water washing, filtration and/or decanting. Often, the chemical conversion is accomplished with a Lewis acid such as stannic chloride, and in some cases the separation effected with an adsorbent such as activated charcoal. These prior art methods have, however, been primarily concerned with the separation of relatively high concentrations of lead (greater than1 gram lead per gallon of gasoline) from relatively small volumes of gasoline and are not ideally suited to use for the separation of relatively small concentrations of lead (less than 0.5 grams lead per gallon of gasoline) from comparatively large volumes of gasoline. Moreover, these prior art processes often result in an undesirable increase in the gum content of the treated gasoline.
More recently, and as is known from copending application Ser. No. 405,124, filed Oct. 10, 1973, it has been discovered that certain activated charcoals, which have been impregnated with a hydrous ferric chloride, can be used to separate organolead compounds from gasoline and many of the aforementioned disadvantages of the prior art processes avoided thereby. The absorption or separation capacity of the ferric chloride impregnated carbons is significantly reduced, however, if the treated gasolines contain relatively large amounts of either light or heavy cat naphthas. As also recently discovered, and known from copending application Ser. No. 458,669, certain activated carbons can be impregnated with cupric chloride and effectively used to separate organolead compounds from gasolines, and these cupric chloride impregnated adsorbents are surprisingly effective when used with gasolines containing light and heavy naphthas. These particular impregnated adsorbents are, however, most effective in separating tetraethyl lead and, while effective with tetramethyl lead and equilibrated mixtures of tetramethyl and tetraethyl leads, they are not as effective with these particular lead compounds as would be desired, generally, in a large scale deleading operation. The need, then, for a separation process geared to the treatment of large volumes of gasoline without substantially increasing the gum content thereof and which can be effectively used with gasolines containing relatively large concentrations of light and/or heavy cat naphthas and for the separation of tetramethyl lead and/or equilibrated mixtures of tetramethyl and tetraethyl leads, is, therefore, believed to be readily apparent.